Research Article: Assessing subcutaneous adipose tissue by simple and portable field instruments: Skinfolds versus A-mode ultrasound measurements

Date Published: November 29, 2018

Publisher: Public Library of Science

Author(s): Carla Pérez-Chirinos Buxadé, Toni Solà-Perez, Jorge Castizo-Olier, Marta Carrasco-Marginet, Alex Roy, Michael Marfell-Jones, Alfredo Irurtia, Adewale L. Oyeyemi.


This study compared subcutaneous adipose tissue (SAT) measurements using a skinfold caliper and Renco Lean-Meater Series 12 A-mode portable ultrasound scanner (A-US). It aimed to assess their inter- and intra-rater reliability and measure the agreement between both methods.

Eighty-four volunteers of different fitness levels were divided into three groups by Ʃ6 skinfolds: G1 ≤ 55 mm (n = 33 males); G2 > 55 mm (n = 32 males); G3 = 98.0 ± 52.3 mm (n = 19 females). Triceps, subscapular, biceps, iliac crest, supraspinal, abdominal, front thigh and medial calf were assessed by ultrasound and skinfolds. Two technicians for both tools performed triplicate measures. Intraclass correlation (ICC), technical error of measurement (TEM) and coefficients of variation (CVs) were applied for test-retest and inter-rater reliability. Non-Parametric statistics were used in order to establish possible statistical differences and correlation between skinfolds thickness and uncompressed subcutaneous adipose tissue thickness from ultrasound. The amount of agreement between both methods was assessed with Lin’s coefficient and a scatterplot of all site locations. A Bland-Altman plot was constructed to establish limits of agreement between groups and regression analysis was employed to assess the ability of skinfolds to explain the variance of ultrasound.

Test-retest ICC for skinfolds and ultrasound were higher than 0.989 and 0.793, respectively. Inter-rater ICC for skinfolds was 0.999 with a 95% CI of 0.995 to 0.999 and for ultrasound was 0.755 with a much larger 95% CI of 0.622 to 0.841. TEMs (> 8.50%) and CVs (> 6.72%) compromised ultrasound reliability. Statistical differences were found in most of the analysed anatomical sites (p < 0.001) except in biceps G2 (Z = -1.150, p = 0.25) and G3 (Z = -1.309, p = 0.19). Good correlations (r > 0.7, p ≤ 0.05) were reported at almost all anatomical sites and groups except for biceps (G1: Rho = 0.26, p = 0.140) and abdominal (G2: Rho = -0.16, p = 0.38; G3: Rho = 0.43, p = 0.068). Lin’s concordance correlation coefficient registered low values of agreement between skinfolds and A-mode ultrasound (ranged from—0.009–0.646). The scatterplot and the estimated regression line drawn through the midst of all anatomical sites of the whole sample had a slope of 0.51 and R2 adjusted = 0.62 was obtained. The combined analysis between the Bland-Altman plot and the linear regression showed that specifically in the G2 and G3 groups, as the SAT increases the differences between skinfolds and ultrasounds measurements also increases.

The Renco Lean-Meater ultrasound is not interchangeable with skinfold measures. Its utility is questionable, particularly for assessing SAT in active adult populations. Its poor test-retest and inter-rater reliability as well as the lack of agreement when compared to the skinfolds would exclude the free use of the A-mode ultrasound scanner in its hypothetical replacing of the classical calipers.

Partial Text

Body composition is a key factor in determining health and sport performance [1–3]. Related to health, the amount and distribution of body fat is an important indicator of disease risk in both individuals and populations. The on-going epidemic of obesity (defined as BMI > 95th percentile) in children and adults has highlighted the significance of excess body fat amounts for short and long term health [4–6]. In regard to sport performance, monitoring body fat in athletes may assess the effectiveness of an exercise or dietary intervention as well as define a performance or selection criterion [3]. Furthermore, in weight-sensitive sports, it may be used to monitor the athletes’ health status because many of them aim for short- term body mass reduction or maintaining a very low weight in order to obtain a competitive advantage [7]. Nevertheless, sometimes these sudden changes may induce severe medical problems such as loss of tissue or insufficient bone mineral density [1,8,9].

Reliability results appear in Table 2. With regard to skinfolds, a high test-retest and inter-rater reliability was obtained. The values obtained in the ICC were very high, with the lowest reported value at 0.989 ICC (95% CI = 0.983–0.993) by Technician 2. The values obtained in the TEM and in the CV also show a high reliability. TEM values were lower than 5% in all anatomical sites with the exception of triceps (9.01%), biceps (6.96%) and supraspinal (6.03%) by Technician 2. CV was inferior to 7% in all anatomical sites. With the highest value reported by technician 2 at the point of the biceps (6.58%).

The purpose of this study was to test the reliability and the degree of agreement of the A- mode portable ultrasound scanner (Renco Lean-Meater Series 12) for assessing subcutaneous adipose tissue in active adult population by comparing it to skinfolds. To our knowledge, this study used the largest and most varied sample to date to compare these two methods at anatomical-site locations.




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